The Aim-quoted company, which last year struck a £6.6 million deal to buy two projects from ScottishPower, has raised about £6.5m through a discounted share placing to help fund its development activities.
Among its schemes are the Meygen project being constructed in the Pentland Firth and a 10 megawatt project in the Sound of Islay, which has secured €21m (£16.6m) of European grant funding.
Atlantis chief executive Tim Cornelius said: “Through this successful placing, both existing and new shareholders have demonstrated their support for Atlantis, our recent achievements and our ambitions for the future – both in the immediate and longer term.
“We look forward to working with our partners to further the development of the tidal stream industry in the UK and beyond.”
The firm, which is due to report its annual results before the end of next month, also told investors today that it was on course to deliver a profit of about £2.7m for 2015, helped by an accounting gain on the acquisition of Marine Current Turbines from Siemens last year.
Earlier this month, Belgian offshore services company Deme said it had agreed to buy a 2 per cent stake in Atlantis’ Tidal Power Scotland arm in a deal that valued the business at £100m.